1. Field of the Invention
This invention relates, in general, to dielectric resonators and more particularly to ring shaped dielectric resonators.
2. Description of Background Art
A typical ring shaped dielectric resonator is tuned by a tuning screw, made of either a metal or dielectric material, from above the dielectric resonator. As the tuning screw is adjusted, the distance between the tuning screw's end and the dielectric resonator varies affecting the electric field of the resonator, which in turn affects the magnetic field of the resonator.
As a signal is processed through the dielectric resonator, four first order modes (TE.sub.01.delta., TM.sub.01.delta., HE.sub.11.delta., EH.sub.11.delta.) are created. Mode TE.sub.01.delta. is considered the fundamental mode and the remaining modes are considered the spurious responses (or spurs), or spurious responses such as TM.sub.01.delta. and HE.sub.11.delta., are created. As the resonator is tuned, the spurious responses move toward the fundamental response, causing distortion of the fundamental response.
In addition, for a ring shaped dielectric resonator to be effective, a very high accuracy, or a very tight tolerance in dimension, is required in the design of the dielectric resonator. This low tolerance is difficult to achieve with present manufacturing capabilities.
Further, in the past resonators have used a large tuning screw to tune the dielectric resonator. These large tuners cause problems when the resonators are required to be close together. Physically it is difficult to access the tuner since the heads of the screws are so close together. In addition, when the resonators are placed close together, tuning one resonator often has a tuning effect on adjacent resonators.